The statements in this section merely provide background information related to the present disclosure and may or may not constitute prior art.
Most types of transmissions include an input shaft, an output shaft, a plurality of gear arrangements, interconnecting members, shafts, and torque transmitting mechanisms among other mechanical members. The various torque transmitting mechanisms are employed to selectively transmit torque from one rotating member to another or from a rotating member to a stationary member to achieve a specific speed ratio between the input and output shafts. The output shaft drives a final drive assembly which may have a further speed ratio change between the transmission output shaft and the axle.
When the need for a power take-off (PTO) assembly or other type of equipment requiring torque for operation arises, power for operation of many common PTO devices is commonly either turbine driven or engine driven. If the PTO is turbine driven, the PTO is driven when the transmission is engaged with a predetermined clutch, or after the torque converter is doing work. If the PTO is engine driven, it is coupled to an input shaft or torque converter hub that is always available when the engine is running and is therefore not limited to a transmission mode. A PTO housing containing the PTO rotating and output connection elements can be connected to the transmission. Lubrication oil must be provided for the rotating elements in the PTO housing.
Known PTO systems are supplied with lubricating oil from a lubrication oil system of the transmission, and retain the lubricating oil for the rotating elements in the PTO housing, with only a “limited return” of the oil to a transmission sump. Oil in the PTO system must essentially fill up most of the PTO housing before it reaches a level required to drain back to the transmission. This results in spin losses and reduced efficiency during PTO component operation as well as during periods when PTO components are not engaged, because the rotating elements of the PTO unit are in continuous rotating contact with the lubricating oil. Known PTO systems also do not provide positive pressurized oil flow to the disconnect clutch, but only provide oil as an oil reservoir.
There is therefore a need for a PTO unit which reduces spin loss and improves efficiency over known PTO units which provide only limited return of lubricating oil to the transmission sump after oil fills to a predetermined height in the unit, and a further need for a PTO unit that provides positive pressure oil flow for lubrication of a disconnect clutch.